resize before/after filtering

[kallenin]

Hi,

Is there a clear cut answer for the question of whether you should filter before or after resize? My instinct is to always filter first (so you process on the original source), but I could see maybe if you were enlarging there might be a case to resize first? Or maybe the difference would be so small it would be like the error you get from color space conversions... Anyway if the order doesn't matter, it would seem that you would prefere filter then resize for enlarging and resize then filter for shrinking since that would decrease the amount of processing.

-Kallenin

[Tack]

I'd say it depends on the filter, but you'll usually want to do it before resizing. Particularly deinterlacing must be done before scaling. You'd want to denoise as well before scaling. On the other hand, I'd probably do color correction after scaling. And obviously any sharpening should be done after scaling (which is a bit redundant to point out given that if you want to apply an unsharp mask it's likely because of the scaling).